Use of organoclay as emulsifier in polymeric gels for water permeability reduction

ABSTRACT

Organoclay is used as an alternative emulsifier and reinforcing agent and to enhance the strength of emulsified polymeric gel aqueous solutions and form water in oil emulsions. The stability of the emulsion can be controlled by controlling salinity and the intensity of initial mixing. The new system can be used for water shut-off treatments as well as a relative permeability modifier in high water permeability zones. In addition, the system can tolerate salts much better than classical surfactants. This system will be appropriate for wellbores having high temperature (&gt; 85 ° C.) with harsh environmental conditions.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an organoclay comprisingDitallow-dimethyl-ammonium salt and a phyllosilicate, an emulsified gelusing the organoclay and a polyethyleneimine cross-linked polyacrylamidechain, and a method for using the emulsified gel.

2. Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Stavland et.al (2006) (Arne Stavland, Knut Inge Andersen, Bernt Sandoey,Tore Tjomsland, Amare Ambaye Mebratu: “How to apply a blocking gelsystem for bullhead selective water shutoff: From Laboratory to field”,SPE 2006) (incorporated herein by reference in its entirety) proposed anew mechanism for water control in oil fields liable to high waterproduction during oil exploration. This new mechanism involved injectingwater-based emulsified gelant into the formation. In theirinvestigation, emulsion was designed such that it separated into a waterphase and oil phase at static conditions in the formation. Following thereaction in the formation, it was expected that the water phase gels upwhile the oil phase remains mobile.

Cross-linked polymeric gels especially polyacrylamide gels are widelyused in petroleum industries to minimize water production during oil andgas exploration and production. Aqueous polymer gels are usuallyemulsified in oil and then injected in the water zones. The purpose ofthe emulsification is to provide open pathways for oil flow. This isbecause in water wet media, the gel formed will block pore throats andreduce the permeability to water and oil. Therefore, oil should form theexternal phase of the emulsion. The emulsion should be injected as onecomponent, and then it will separate into oil phase (for oil flow) andwater phase. The water phase contains the gelant which will gel up in aportion of the pore space to reduce permeability to water. Surfactantsare usually used to emulsify the aqueous gel solution in oil.

Gelled or cross-linked water soluble polymers are widely used in manypetroleum industries to reduce water production from high permeabilityzones in wellbores and increase oil production. For instance, suchgelled polymers can be utilized to change the permeability ofunderground formations. In several water shut-off applications, polymersand suitable crosslinking agents or systems are pumped in an aqueoussolution into the underground formation. The polymers permeate intoregions having the highest water permeability and gel therein.

BRIEF SUMMARY OF THE INVENTION

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

One embodiment of the disclosure relates to an organoclay comprisingDitallow-dimethyl-ammonium salt and a phyllosilicate.

In another embodiment, the ammonium salt in the organoclay is ammoniumchloride and the phyllosilicate in the organoclay is sodium bentonite.

In another embodiment, the organoclay has a density of 1.6-1.8 kg/m³.

In another embodiment, an emulsified gel comprises the organoclay, apolyethyleneimine cross-linked polyacrylamide chain, an oil, and water.

In another embodiment, the emulsified gel further comprises thepolyethyleneimine cross-linked polyacrylamide chain with 3-10% wtpolyacrylamide and 0.3-1.2% wt polyethyleneimine.

In another embodiment, the polyethyleneimine cross-linked polyacrylamidechain and oil have a volume ratio of 60-80% polyethyleneiminecross-linked polyacrylamide chain and 40-20% oil.

In another embodiment, a method for using the emulsified gel comprisespreparing an emulsified gel solution comprising polyethyleneiminecross-linked polyacrylamide chain, water and diesel injecting the gelinto a well to modify the permeability of a porous formation surroundingthe well.

In another embodiment the wellbore has a temperature greater than 85° C.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 depicts an example of water-in-oil emulsion;

FIGS. 2A-2B depict an emulsion stability drop test;

FIGS. 3A-3B depict produced emulsified gel solutions with organoclay andsurfactant;

FIG. 4 is a graph of the storage modulus as a function of time ofemulsified gels developed using distilled water;

FIG. 5 is a graph of the storage modulus as a function of time ofemulsified gels developed using seawater;

FIGS. 6A-6B depict the droplet size distributions of emulsified gelcontaining the surfactant and the organoclay at room temperature;

FIGS. 7A-7B depict the droplet size distributions of emulsified gelcontaining the surfactant and the organoclay at temperature of 50° C.;

FIG. 8 is a graph of the phase behavior of the emulsified gel systemcontaining the organoclay in seawater;

FIG. 9 is a graph of the phase behavior of the emulsified gel systemcontaining organoclay in seawater; and

FIGS. 10A-10B depict the droplet size distributions of emulsified gelcontaining the organoclay at room temperature.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views.

One embodiment of the invention includes a method of making anemulsified gel solution. A water in oil emulsion is prepared bydissolving a surfactant into a diesel solution to create a mixture. Thesurfactant, also known as an emulsifier, is preferably an oil solublesalt. More preferably, the surfactant is a tallowamine acetate salt.

In another embodiment, Polyacrylamide (PAM) and polyethyleneimine (PEI)are used as emulsifying agents. PEI is used as the cross-linking agentto form a PAM/PEI cross-linked chain.

Cross-links are formed by chemical reactions that are initiated by heat,pressure, change in pH or radiation. In one embodiment, mixing of anunpolymerized or partially polymerized resin with cross-linking reagentsresults in a chemical reaction that forms cross-links. Cross-linking canalso be induced in materials that are normally thermoplastic throughexposure to a radiation source, such as electron beam exposure,gamma-radiation, or UV light. For example, electron beam processing isused to cross-link the C type of cross-linked polyethylene. Other typesof cross-linked polyethylene are made by addition of peroxide duringextruding (type A) or by addition of a cross-linking agent (e.g.vinylsilane) and a catalyst during extruding and then performing apost-extrusion curing.

In one embodiment of the invention, the cross-linking of PAM and PEIoccurs as a mixture is injected into a well. The mixture that isinjected into the well comprises PEI, PAM and organoclay. The PAM iscross-linked with PEI as both polymers are injected into the well.

In another embodiment, PAM and PEI are cross-linked to form across-linked PAM/PEI polymer solution prior to injection into the well.The water in oil emulsion is then mixed with the cross-linked PAM/PEIsolution and is then subjected to agitation to create a homogenousmixture of the compounds. Manual methods and mechanical methods may beused to mix the solution. Manual methods of mixing may be used to mixthe solution including but not limited to swirling the solution by handand by placing a magnetic stir bar in the solution and stirring with amagnetic stir plate. Mechanical methods include but are not limited tosonicating the solution using an ultrasonic bath or an ultrasonic probe,ultrasonicating the solution, or using a high power homogenizer.Preferably, a high power homogenizer is used to agitate the mixture. Themixture is mixed in the homogenizer at a power in the range of 30-100Hz, 40-80 Hz, or 50-60 Hz. Preferably, the mixture is mixed in thehomogenizer at a power in the range of 50-60 Hz. The homogenizerfunctions at a power within the range of 800-1500 W, 900-1300 W, or1000-1200 W. More preferably, the homogenizer functions at a powerbetween 1000-1200 W. The speed of agitation in the homogenizer is in therange of 2000-5000 rpm, 2500-4500 rpm, or 3000-4250 rpm. Preferably, thespeed of agitation is 4000 rpm. The solution is homogenized at a timeperiod ranging from 10-50 minutes, 15-40 minutes, and 20-30 minutes.Preferably, the solution is homogenized continuously for 30 minutes.

Following mixing of the surfactant and diesel solution, brine solutionis added gradually to the mixture. The brine solution is added at avolume in the range of 5-30 kppm NaCl, 10-25 kppm NaCl, or 15-20 kppmNaCl. Preferably, the brine solution is added at a volume of 20 kppmNaCl.

The concentration of PAM in the emulsified aqueous gel solution is 3-15%wt, 4-12% wt, or 4-10% wt. Preferably, the concentration of PAM in theemulsified aqueous gel solution is 7% wt. The concentration of PEI inthe emulsified aqueous gel solution is 0.001-2% wt, 0.01-1.5% wt, or0.02-1.0% wt. Preferably, the concentration of PEI in the emulsifiedaqueous gel solution is 0.3% wt.

The diesel to gel solution formation ratio may range from 10% diesel and90% gel solution, 20% diesel and 80% gel solution, 30% diesel and 70%gel solution, and 50% diesel and 50% gel solution. Preferably, thediesel to gel solution formation ratio is 30% diesel and 70% gelsolution.

In another embodiment, two emulsified gel solutions are prepared usingdistilled water. The first emulsified gel solution includes thesurfactant with a total sample volume in the range of 0.1-5%, 0.2-4%, or0.3-3%. Preferably, the emulsified gel solution includes the surfactantwith a total sample volume of 0.5%.

The second emulsified gel solution includes an organoclay that is usedin place of the surfactant. The organoclay is aditallow-dimethyl-ammonium salt mixed with a phyllosilicate. The saltmay include but is not limited to ammonium chloride, ammonium carbonate,and ammonium nitrate. Preferably, the ammonium salt is ammoniumchloride. Phyllosilicates include but are not limited to antigorite,chrysotile, lizardite, halloysite, kaolinite, illite, montmorillonite,vermiculite, talc, palygorskite, pyrophyllite, biotite, muscovite,phlogopite, lepidolite, margarite, glauconite, chlorite, sodiumbentonite, calcium bentonite, and potassium bentonite. Preferably, thephyllosilicate used is sodium bentonite. More preferably, the organoclayis a ditallow-dimethyl-ammonium chloride mixed with sodium bentonite.

The second emulsified gel solution includes the organoclay with aconcentration in the range of 300-1000 ppm, 400-800 ppm, or 450-750 ppm.Preferably, the second emulsified gel solution includes the organoclaywith a concentration in the range of 500 ppm. The droplet sizedistribution of the emulsified gel including about 500 ppm with anagitation speed of about 1000 rpm is in the range of 10-20 μm. Morepreferably, the droplet size is about 18 μm.

The present disclosure relates to the significance of organoclay as analternative emulsifier and reinforcement agent. The organoclay basedemulsifier enhances the strength of emulsified polymeric gel aqueoussolutions and forms water in oil emulsions. The stability of theemulsion may be controlled by controlling the salinity and the intensityof initial mixing. The system demonstrates promising gel strength andmay be used for water shut-off polymeric gels as well as a relativepermeability modifier in high water permeability zones. In addition, thesystem can tolerate salts much better than classical surfactants. Thisgel will be appropriate for wellbores having high temperature (>85° C.)with harsh environmental conditions.

However, there are situations during oil recovery where selective watershut-off is desirable and not total water shut-off. In this type ofscenario, emulsified gel systems having considerable strength will bemore efficient and effective. Hence, the emulsified gel of the currentdisclosure is appropriate for selective water blockage in regions havinghigh permeability. Water based gellant is emulsified in oil and theninjected into the formation. The emulsion is formulated and designed toseparate into a water phase and oil phase at static conditions in theformation. Following the reaction in the formation, it is expected thatthe water phase gels up while the oil phase remains mobile. Thecontrolling parameter for disproportionate permeability reduction (DPR)is the control of the fraction of gel occupying the porous media. Thewater fraction in the emulsion controls the reduction in relative oiland water permeability.

One reliable method to achieving water cut in the high permeabilityzones is to use emulsified gel aqueous solution in oil with substantialgel strength. The disclosure describes an emulsified gel prepared bymixing polyacrylamide gel solution/oil (diesel) in the volume ratio of70/30 containing suitable amount of surfactant (emulsifier). Anothertype of emulsified gel involves agitation of polyacrylamide gelsolution/oil (diesel) in the volume ratio of 70/30 containing organoclayof appropriate quantity. The purpose of using organoclay is to replaceor act as a substitute for classical surfactants used in suchapplications such as AKzoNobel Armac T. The new emulsifier enhances theproperties of emulsified gel solutions and improves the gel strength.Distilled water and seawater are employed for the preparation of allemulsified gels in the current disclosure.

Currently, many nanomaterials are developed for several applications invarious fields of endeavors. Layered silicate clay minerals are one ofthe most well-known nanomaterials due to their availability, low costand more importantly environmentally friendly. The choice of organoclayin the embodiment of this disclosure includes its availability and highsurface area of the dispersed nano-sized particle. Hence, the embodimentof this disclosure highlights the use of organoclay as emulsifier foroptimal emulsified gel system performance in water shut-off applicationsduring oil and gas exploration and production.

The surfactant (also known as emulsifier, ARMAC T) is used as areference for comparison. The criteria for the selection were (i) oilsolubility (ii) easy to mix in oil (iii) controllable separation timeand (iv) friendly to environment. This surfactant is primary tallowamineacetate salt and is usually used as well as other surfactants for waterin oil emulsions used in acid stimulation jobs ((Nasr-El-Din et al.,2006; 2007; Liang Xu, 2013). The use of surfactants to emulsify a gelantfor permeability reduction was also studied in a previous patent (ArneStavland, Sandnes (NO), Svante Nilsson, Jarfalla (SE): “Emulsifiedgelant”, US 2008/0009424A1). An oil soluble surfactant was used. Inanother publication, alchol-etoxylate and fatty acid amine were used forgelant emulsification (Arne Stavland, Knut Inge Andersen, Bernt Sandoey,Tore Tjomsland, Amare Ambaye Mebratu: “How to apply a blocking gelsystem for bullhead selective water shutoff: From Laboratory to field”,SPE 2006). Both the physical and chemical properties of the surfactantchosen for this invention are given in Table 1. The use of thissurfactant is not limited to the findings of this embodiment. It canalso be used as a dispersing agent; adjuvant; mineral/pigment;dispersant and flocculating agent. Thus, its applications are not in anyway limited to the findings of this disclosure.

The key factors in the selection of oil for this invention wereavailability, viscosity, safety and price. Diesel was selected becauseit satisfies all of these requirements. The diesel employed was obtainedfrom a local gas station in Saudi Arabia. Furthermore, organoclay waschosen as a potential emulsifier because of its inherent properties. Itsapplication as an emulsifier for emulsified gel system in water shut-offis the main focus of this disclosure. The physical properties oforganoclay employed in this disclosure are shown in Table 2.

EXAMPLES

Water in oil emulsion was prepared by first dissolving the surfactantinto diesel followed by subjecting the mixture to agitation for fewminutes. Afterwards, a measured volume of 20 kppm NaCl brine solutionwas added gradually. The emulsification process was performed using ahigh power homogenizer (Ultra Turrax T 50 basic, WERKE IKA, Germany).The speed of agitation was 4000 rpm. The agitation was continuous for 30minutes. The image of the prepared water-in-oil emulsion is shown inFIG. 1.

Table 1 is a table describing the chemical and physical properties ofthe surfactant. Table 2 is a table describing the physical properties ofthe organoclay. Table 1 and Table 2 are presented below.

TABLE 1 Chemical and physical properties of Surfactant (Trade name:ARMAC T) Solubility in water at 25° C. Isopropanol ethanol, hexane (35°C.) HLB value 6.8 Davies Scale 0-40 pH 6-9 Vapor pressure <1 mmHg @20°C. Pour point  65° C. Flash point 150° C. Melting point  55° C.Appearance Solid at 25° C. Equivalent mass 324 Specific gravity  0.845

TABLE 2 Physical properties of organoclay (Trade name: Cloisite 15A)Product name Ditallow-dimethyl-ammonium salts with Bentonite SupplierSouthern Clay Products, Inc. Description Cream powder Specific density1.6-1.8 Solubility Oil soluble

To ascertain that the produced emulsion was water-in-oil, the drop testwas conducted. Oil (diesel) before addition of emulsion is shown in FIG.2A while FIG. 2B confirms that the emulsion is water-in-oil since it diddisperse in oil (diesel). In furtherance to ensure that the emulsionproduced is water-in-oil-emulsion, a conductivity test is used to checkthe external phase of this emulsion. The result shows that the emulsionhad 0μS/cm conductivity. This observation provided extra proof that theexternal phase is the non-conductive oil rather than the conductivebrine solution.

Moreover, the embodiment of this disclosure also includes preparation ofan emulsified gel aqueous solution. The preparation procedure involvesthe use of polyacrylamide (PAM) and polyethyleneimine (PEI) ascross-linker. The choice of choosing PAM and PEI is attributed to theirblocking effect and the good thermal history. The developed gel solutionincludes PAM and PEI at concentrations of 7.0wt % and 0.3wt %,respectively. The diesel to gel solution formulation ratio is 30/70.

Two emulsified gels were prepared using distilled water. The firstemulsified gel formulation contains surfactant (emulsifier) of 0.5% oftotal sample volume (0.125 ml) while the second emulsified gelformulation contained organoclay with a concentration of 500 ppm.

Another two sets of emulsified gels were again prepared using seawater.A set contains surfactant (emulsifier) of 0.5% of total sample volume(0.125 mL) while the other contains organoclay with a concentration of500 ppm. All emulsified gel formulations used in this disclosure wereobtained by mixing 7.0 wt % PAM and 0.3 wt % PEI in either distilledwater or seawater for 10 minutes. Diesel of 30% by volume is mixed withthe gel solution. Diesel was added to the gel to obtain the requiredgel/oil ratio. The mixture was then subjected to another 30 minutes ofagitation after which emulsified gel solution was formed. The producedemulsified gel is displayed in FIGS. 3A-3B. FIG. 3A depicts theemulsified gel solution with the organoclay and FIG. 3B depicts theemulsified gel solution with the surfactant.

The produced emulsified gels were characterized by a TA hybrid rheometerequipped with pressure cell allowing measurements at higher temperature.The emulsified gels were pressurized with nitrogen gas in order to expeloxygen and to prevent the gel system from evaporation during rheologicalmeasurement. The operating pressure was 500 psi. Oscillatorymeasurements on the gel solution were performed at 120° C., a strain of10% and a frequency of 1 Hz.

Emulsified gels in distilled water (DW) are shown in FIG. 4. FIG. 4 is agraph of the storage modulus as a function of time of emulsified gelsdeveloped using distilled water. The use of surfactant in the emulsifiedgel produced a storage modulus of 380 Pa, whereas, using organoclay asan emulsifying agent resulted in a storage modulus of 428 Pa with anincrease of 11% after˜600 minutes. As such, organoclay can be utilizedas an additive to reinforce the gel system for water shut-off inwellbores having high permeability zones.

For comparison, seawater (SW) was also used to develop emulsified gels.FIG. 5 is a graph of the storage modulus as a function of time ofemulsified gels developed using seawater. From FIG. 5, the emulsifiedgel containing surfactant achieved a storage modulus of 569 Pa while theemulsified gel system containing organoclay had a storage modulus of 703Pa after˜600 minutes. The emulsified gel system containing 500 ppmorganoclay showed better performance in storage modulus. The emulsifiedgel developed using organoclay had higher storage modulus thanemulsified gel containing surfactant. The difference in their strengthwas about 19%. It was very clear that emulsified gel prepared fromseawater containing 500 ppm organoclay exhibited higher storage modulus.The droplet size of emulsified developed gels, as observed under theelectron microscope, is shown in FIGS. 6A-6B. FIG. 6A is a micrograph ofthe emulsified gel containing the surfactant agitated at 400 rpm. FIG.6B is a micrograph of the droplet size distribution of emulsified gelcontaining 500 rpm organoclay agitated at 4000 rpm. The addition of theorganoclay resulted in very small droplet size which was likely thereason for the stability of the emulsion. The concept behind thetechnology of emulsified gelant for DPR is based on controlling thegelant saturation in the target zone. One method to achieve this taskwas to emulsify the gelant in oil or diesel. First, the gelant wasprepared by adding the required amount of polymer and cross-linker towater. Then, oil or diesel was added to obtain the desired water to oilratio. A quasi-sable emulsion was formed by adding a suitableemulsifier. After injection and well shut-in, the emulsion wouldseparate into two phases. The oil phase maintains the flow for oil,while, the water phase containing the gelant gels up in some fractionsof the pore and reduce permeability to water. There are importantrequirements for successful application of emulsified gelant. Theinjection and separation time should be lower than the gelation time.

Thus, the phase separation behavior of emulsified gel containing 500 ppmorganoclay in seawater was monitored. It should be pointed out that thisparticular emulsified gel system was agitated at a speed of 1000 rpmwhereas all previously mentioned gel systems in this invention wereagitated at 4000 rpm. The interesting observations here include: (i)application of organoclay as a substitute for emulsifier in preparingemulsified gel as the stability of produced emulsions using emulsifiertends to be weak, (ii) emulsified gel system produced using organoclayachieved good stability at room temperature and this means that thissystem will separate quickly at high temperature (>85° C.). To confirmthat these emulsified gel systems will separate at higher temperature,droplet sizes of each separate emulsified gel containing surfactant and500 ppm organoclay were viewed under electron microscope having heatingdevice with flat glass surface. Each gel system was placed on the flatglass surface and heated up to 50° C. It was observed that the dropletsizes of these systems were larger than the droplet sizes shown in FIGS.6A-6B. The large droplet size suggests reduced stability of thesesystems and consequently short separation time was observed withincreased temperature. At this temperature (50° C.); the separation timeof the gel system containing organoclay was shorter than the gel systemcontaining surfactant. As a result, organoclay gel system with 500 ppmorganoclay is expected to separate faster than surfactant gel systembefore gelation process begins. The droplet size images at 50° C. forboth emulsified gel systems are given in FIGS. 7A-7B. FIG. 7A is amicrograph of the emulsified gel containing the surfactant at 50° C. and1000 rpm. FIG. 7B is a micrograph of the droplet size distribution ofthe emulsified gel containing 500 ppm of the organoclay at 50° C. and1000 rpm. The phase behavior versus time at room temperature for the twoemulsified gel systems was displayed in FIG. 8. FIG. 8 is a graph of thephase behavior of the emulsified gel system containing 500 ppmorganoclay in seawater conducted at room temperature and 1000 rpm. Atroom temperature, the water phase fully separated out within 25-33minutes. The emulsified gel system was regained when subjected toagitation again at a speed of 1000 rpm. In spite of using 1000 rpm, theemulsified gel solution was stable as the droplet sizes were small. Thisobservation suggested that organoclay could act as emulsifier in theformulation of the emulsified gel systems used in water permeabilityreduction.

In the real field operation, the emulsified gel system is expected toseparate before the beginning of the gelation process. So, theseparation time should be less than the gelation time. However, theseparation should not be too fast or spontaneous. Since the separationtime of gel system containing 500 ppm organoclay lasted for just 33minutes, it was decided to increase the concentration of organoclay to1000 ppm and then study the phase behavior of this system once again.The water-oil phase fully separated after 115 minutes. It should bementioned that the phase separation was conducted at room temperatureand 1000 rpm. The phase behavior versus time of the emulsified gelsystems containing 1000 ppm organoclay is shown in FIG. 9. FIG. 9 is agraph of the phase behavior of the emulsified gel system containing 1000ppm organoclay in seawater conducted at room temperature and 1000 rpm.The droplet size of the emulsified gel solution containing 500 ppm and1000 ppm organoclay are displayed in FIGS. 10A-10B. FIG. 10A is amicrograph of the emulsified gel containing 500 ppm organoclay viewed atroom temperature and 1000 rpm. FIG. 10B is a micrograph of the dropletsize of the emulsified gel containing 1000 ppm organoclay viewed at roomtemperature and 1000 rpm. The gel system containing 1000 ppm organoclayproduced droplets that were very small which explained the observed longseparation time. Therefore, the addition of the organoclay may be usedto improve the gel strength as well as control the separation time at aspecific reservoir temperature.

The embodiment of this disclosure highlights the significance oforganoclay as emulsifier for water shut-off treatment in petroleumindustries. This disclosure may be useful in petroleum and oil servicecompanies. The emulsified gels developed may be suitable for theselective water shut-off in wellbores having high permeability and theemulsion stability can be controlled by using the dose of the organoclayor by controlling the intensity of the initial mixing.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, define, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

1. An organoclay comprising Ditallow-dimethyl-ammonium salt and aphyllosilicate.
 2. The organoclay of claim 1 wherein the ammonium saltis ammonium chloride and the phyllosilicate is sodium bentonite.
 3. Theorganoclay of claim 1 wherein the organoclay has a density of 1.6-1.8kg/m³.
 4. An emulsified gel using the organoclay of claim 1, comprising:a polyethyleneimine cross-linked polyacrylamide chain; an oil; andwater.
 5. The emulsified gel of claim 4 wherein: the polyethyleneiminecross-linked polyacrylamide chain is-3-10% wt polyacrylamide and0.3-1.2% wt polyethyleneimine; and the polyethyleneimine cross-linkedpolyacrylamide chain and oil have a volume ratio of 60-80%polyethyleneimine cross-linked polyacrylamide chain and 40-20% oil.
 6. Amethod for using the emulsified gel of claim 4, comprising: preparing anemulsified gel solution comprising polyethyleneimine cross-linkedpolyacrylamide chain, water and diesel; and injecting the gel into awell to modify the permeability of a porous formation surrounding thewell.
 7. The method of claim 6, wherein the wellbore has a temperaturegreater than 85° C.